1. Field of the Invention
The present invention relates generally to apparatus and methods used in assessing a person's hearing acuity and more specifically to audiometric apparatus and methods that produce and involve the production of synthetic speech sounds.
2. Description of the Prior Art
Traditionally, the evaluation of a person's hearing acuity and the determination of the site of lesion in persons with auditory pathologies has been accomplished in the field of audiology using an audiometer that can be operated in either a pure-tone or speech mode. While in the pure-tone mode, such an audiometer, known as a pure-tone and speech audiometer, is capable of producing pure tones, i.e., tones of a single frequency, at octave intervals. The frequency, sound pressure level (SPL) and the duration of such tones are controllable by the operator of the audiometer. According to ordinary audiological techniques involving the production of pure tones, the patient is asked to give a signal whenever he hears a pure tone generated by the audiometer. While the audiometer is in the speech mode, the operator of the audiometer pronounces common words, usually one or two syllable words, into a microphone. The sound of such words is reproduced by the audiometer in substantially their original form although the loudness of the reproduced sound is controllable by the operator. According to standard audiological techniques, the patient is requested to identify the word reproduced by the audiometer.
Many pure-tone and speech audiometers are also capable of producing white noise simultaneously with or separate from the speech or pure-tone sounds. Ordinarily, such white noise is used to mask the pure tone or speech sounds in order to evaluate the patient's ability to discriminate such sounds from the white noise.
A problem with the pure-tone and speech audiometer is that it basically assesses audition using only a very rudimentary (pure-tone) or an extremely complex (speech) sound. Such an audiometer and the techniques associated therewith provide little flexibility for evaluating a person's auditory behavior between those two levels of functioning. Thus, while such an audiometer is sufficient to provide audiometric data for the majority of patients seen in a routine diagnostic examination, something more is needed for other patients such as those that are difficult to test, those with a severe or profound hearing impairment and those with central auditory processing problems. In addition, the specific frequencies used for testing with such an audiometer may not be those to which these special cases are most sensitive.